A continuation of efforts funded under HD-10267 for support of population studies of Mormon genealogies, this project differs from previous work in focusing upon a single issue, the fertility transition, and in seeking funding for further data extension and evaluation. The Mormon historical demography project is part of a comprehensive effort at the Univ. of Utah involving the collaboration of scholars from genetics, demography, medical sciences, and computer science. Common to all projects is the use of a single data base derived originally from approximately 170,000 three generation family group sheets maintained by the Genealogical Society of Utah. The data base is being extended by the addition of new group sheets, death and birth certificates for the State of Utah (from 1905), tumor registry and other data sets which support medical projects designed to investigate genetic factors in disease transmission. The demography program complements those activities through its overall goal of providing a comprehensive historical-demographic evaluation and analysis of the Utah population and their ancestors. This grant specifically proposes to investigate the fertility transition of the Utah population from patterns of natural fertility through periods marked by control, with a time frame of approximately 100 years. Three major propositions are proposed for investigation: the pattern of natural fertility was an emergent condition; it was a nonhomogenous pattern; and the transition represented the adaptation to changing social and economic conditions. Tests of the shift from natural to controlled fertility involve the investigation of age patterns of fertility for the population disaggregated by religion, religious commitment, origin, type of residence, migration history, and occupation - over time. Additional investigations involve the use of macro-simulation methods. Our population also enables us to investigate the effect of polygyny on age of marriage and levels of fertility. To increase the explanatory variables included in the data, to ground our population in time and place, and to provide an external, independent data set for further evaluation of the data set, it is proposed to enter and link the 1880 manuscript census. To accomplish the linking a new general computerized record linking system will be developed.